St. Brigid was seemingly born nearby and graveyard/abbey is where St. Brigid became a nun.
Underneath the hill was the Sli of Brí Ele.
From Mythic Ireland
"In early literature, Ele is represented as a maiden and goddess of awe-inspiring beauty. Every year one of Finn's young men went out from the Hill of Allen to meet her and was lost for ever, in her síd beneath Croaghan Hill.
The Dindshenchas stated that the source of the River Shannon was under Brí Ele at a well called Linn Mna Feile 'the Pool of the Modest Woman'."
It is also associated with the underworld and being sucked into the hill. The cairn on top is meant to have been the entrance to a volcano.
Brigits sister (part of the triple goddess), Begoibne had her smithy workshop beneath the hill and built beautiful cauldrons.
He also states that winter solstice sunrise is visible over Cloghan hill from the Hill of Uisneach.
This well is around to the north side of the hill opposite the village of Cloghan. It is called a St. Patrick's well, but it has a Bridget's cross and statutes and dedications to her.
I would have to speculate that this was originally and Bridget's well that was taken over and rededicated to St. Patrick.
The best way up to the mound is from Carbury Village itself. Across from the shop there is a little lane which leads up to a few fields which have been used for show-jumping. Follow the gravel path here and then through the fields to the top. Again the views are amazing across the bog of allen and the feeling of this being an island is even more than on the top of the Hill of Allen. This must have been a very important hill as its is the only good land in the area.
To me the mound makes the hill look like the belly of the goddess or possibly her nipple. Ive no idea of the age of this mound so I cant comment on whether it is recent or ancient.